Superconductivity in Ni-Doped Ba–Fe–As Thin Films Prepared From Single-Crystal Targets Using PLD

In this paper we report on the structural and superconducting properties of an epitaxially grown Ba(Fe
_1-x
Ni
_x
)
₂
As
₂
thin film using pulsed laser deposition. As target we used an optimally Ni-doped single crystal prepared from self-flux. The superconducting transition temperature of 21.4 K is among the highest values reported for Ni doping exceeding the critical temperature of the single-crystal target. The upper critical field shows a very high slope, which is connected to two-dimensional effect. Transmission electron microscopy investigations indicate planar defects, which might be the origin of this behavior.